Color images formed in silver halide color photographic materials are often stored under exposure to light for a long period of time or are sometimes stored in the dark for a long period of time. It is known that the color images often seriously fade, depending upon the storage conditions, which are determined by the wavelength of light as applied thereto and the amount of the light as well as the surrounding heat, moisture and oxygen. In general, the color fading in the former case is called "light-fading" and that in the latter case "dark-fading". When color photographic materials after being processed are stored as recording media for a long period of time, it is desired that the degree of such light-fading or dark-fading is minimized to the least, i.e., the light fastness and the dark fastness are elevated. Additionally, it is desired that the degree of fading, if any, of the respective colors of yellow, magenta and cyan of the color images in the photographic material is well-balanced. However, there is known a disadvantageous phenomenon that the respective colors of yellow, magenta and cyan of photographic color images differ from one another in their degree of light fastness and dark fastness of the respective colors so that, after the color images have been stored for a long period of time, the systematic color balance of the said three colors in the color images is lost and the image quality on the color reproduction and gradation reproduction is thereby be deteriorated.
In general, the degrees of light-fading and dark-fading differ, depending upon the couplers used as well as other various factors. However, with respect to the dark-fading for dyes which have heretofore been used in many color photographic materials, it is known that the color fading is more noticeable in a cyan color image and then a yellow color image and a magenta color image in this order, and in particular, the degree of the dark-fading of a cyan color image is the most noticeable as compared with the other color images.
Under the circumstances, it is believed necessary to suppress the dark-fading of the cyan color image as much as possible, so as to maintain the initial color balance of the three colors of yellow, magenta and cyan in color images, even after the images have been faded by storage for a long period of time. Therefore, various studies have hitherto been made for improvement of the light-fading and dark-fading of color images, especially the cyan color image. The studies may be grouped into the following two areas. One is to develop new couplers capable of forming color images which hardly fade. The other is to develop new additives capable of inhibiting fading of the color images formed.
Many phenol cyan couplers for forming cyan dyes are known. For example, 2-[.alpha.-2,4-di-tert-amylphenoxybutanamido]-4,6-dichloro-5-methylphenol described in U.S. Pat. No. 2,801,171 may form a color image with a good light fastness. However, this coupler is known to have a defect in that the heat resistance is poor.
Phenol couplers where the 3- or 5-position of the phenol nucleus is substituted by an alkyl group having 2 or more carbon atoms are described in, for example, U.S. Pat. No. 3,772,002 and JP-A-60-209735 and JP-A-60-205447 (the term "JP-A" as used herein refers to a "published unexamined Japanese patent application"). Although the cyan images formed from these couplers have, to some degree, improved dark fastness, it is known that not only the improvement of the dark fastness is not completely sufficient but also the light fastness is inferior to that of the image obtainable from the aforesaid cyan coupler.
2,5-Diacylaminophenol cyan couplers where the 2- and 5-positions of the phenol nucleus are substituted by acylamino groups are described in, for example, U.S. Pat. Nos. 2,369,929, 2,772,162, 2,895,826, and 4,009,035, JP-A-53-109630 and JP-A-55-163537. These 2,5-diacylaminophenol couplers may form cyan images having an extremely good dark fastness. However, these couplers still have some drawbacks in that the light fastness of the cyan images formed therefrom is far inferior to that formed from the aforesaid two cyan couplers. Further, when these couplers are used in printing photographic materials, the color hue of the color images formed therefrom is somewhat shifted to a shorter wavelength range. In order to compensate for the drawbacks, use of the couplers combined with the aforesaid two cyan couplers has been proposed. However, this is known to cause a noticeable lowering of the dark fastness of the color images obtained.
1-Hydroxy-2-naphthamide cyan couplers are generally insufficient in the light fastness.
The 1-hydroxy-2-acylaminocarbostyryl cyan couplers described in GB Patent 2,068,943 may form color images having good fastness to light and heat, but it has been found that the spectral absorption characteristic of the color images formed is unfavorable for color reproduction of color photographs and the color images formed have pink stains after being exposed to light. Thus, these couplers have been found to have various troublesome problems.
The cyan polymer couplers described in U.S. Pat. No. 3,767,4125, JP-A-59-65844 and JP-A-61-39044 are surely excellent in the dark fastness under a low moisture condition, but these couplers have been found defective in that the dark fastness under a high moisture condition is insufficient.
U.S. Pat. No. 4,203,716 discloses a method of dissolving a hydrophobic substance, such as an oil-soluble coupler in a water-miscible organic solvent and blending the resulting solution with a loadable polymer latex so as to load the hydrophobic substance onto the polymer. However, there is a problem that such a method using a loadable polymer latex is inferior to the case of using a water-immiscible high boiling point organic solvent with respect to the light fastness of the cyan image formed. Moreover, a large amount of a polymer is required to be used in order that the coupler is sufficiently loaded to obtain a sufficient maximum color density. Accordingly, still another defect has been found in the above method, i.e., the cost and the film thickness of the photographic materials have to be elevated because of the use of such excess polymers.
JP-B-48-30494 discloses that photographic materials containing an emulsified dispersion of a coupler formed by the use of a homopolymer of organic solvent-soluble hydrophobic monomers having a particular structure or a copolymer of the said monomers with hydrophilic monomers having a particular structure, in place of using any high boiling point organic solvents, have been improved with respect to the hardness, recoloration failure, light fastness and the storability before processing (the term "JP-B" as used herein refers to an "examined Japanese patent publication"). However, it has been found that the use of such homopolymer of hydrophobic monomers in place of high boiling point organic solvents involves various problems in that the coloring capacity of the coupler is poor. This is especially noticeably when the photographic material is processed with a benzyl alcohol-free developer. Further, the stability of the emulsified dispersion during storage is poor.
In addition, another serious problem has also been found in that when the technique as illustrated in JP-B-48-30494 is applied to a cyan coupler, the light fastness of the color image obtained is far worse than the case using an emulsified dispersion obtained by the use of conventional high boiling point organic solvents.
As mentioned above, the couplers whose dark fastness has been improved by variation of the coupler structures by the prior art techniques are noted to be frequently insufficient in terms of the color hue, coloring capacity, generation of stains and, especially, light fastness. Accordingly, a novel technique capable of overcoming all of the prior art problems and satisfying the necessary points mentioned above is being earnestly desired.
On the other hand, benzyl alcohol is widely used in color development of silver halide color photographic materials using conventional oil-protected couplers in order to elevate the coloring capacity and to shorten the processing time.
However, since benzyl alcohol is hardly soluble in water, solvents such as diethylene glycol, triethylene glycol or alkanolamines are necessary so as to easily dissolve the same. These compounds (solvents) and benzyl alcohol have a high BOD value (biological oxygen demand value) and COD value (chemical oxygen demand value) which mean environmental pollution loads. Therefore, use of such compounds and benzyl alcohol is unfavorable in view of prevention of environmental pollution.
Moreover, use of benzyl alcohol has still another unfavorable problem in that a longer time is required for dissolution of the same even when the said solvents are used.
Further, when benzyl alcohol is brought into a bleaching bath or bleach-fixing bath, a leuco form of a cyan dye is easily formed. This causes lowering of the color density of the images formed In addition, benzyl alcohol often causes retardation of the washing out speed of the development components so that it often has a bad influence on the image storability of the photographic materials processed. For these reasons, it is not better to use benzyl alcohol.
Hence, development of couplers and emulsified dispersions containing the same are being desired for the purpose of attaining improvement of the storability of color images and of attaining excellent coloring capacity of couplers even in the absence of benzyl alcohol.
On the other hand, it has additionally been found that the above-mentioned couplers capable of forming color images with an excellent color fastness, as well as the emulsified dispersions containing the same, often have an action on the silver halide emulsion which affects the photographic sensitivity thereof. That is, it has been found that the use of the aforesaid phenol cyan couplers sometimes causes lowering of the color sensitizing sensitivity in silver halide emulsions and the use of magenta couplers or yellow couplers of some kinds also often causes similar desensitization. The technique of improving color image fastness is desired not to bring such action, and, therefore, development of emulsions which are hardly affected by such action is also desired.
JP-A-51-19534, JP-A-51-110327, JP-A-51-134627, JP-A-52-102722 and JP-A-55-64236 describe the same as in the aforesaid JP-B-48-30494. That is, these references describe examples of using organic solvent-soluble polymers having a particular structure in place of high boiling point organic solvents. In all cases, however, when such polymers were applied to cyan couplers, as opposed to dispersion by the use of conventional high boiling point organic solvents, the following problems occurred.
(1) Couplers easily deposit when these are in the form of an emulsion. (2) The coloring capacity is poor. (3) The light fastness of the color images obtained is poor.
On the other hand, U.S. Pat. No. 4,201,589 describes an example of using dibutyl phthalate as a high boiling point solvent. However, when a high boiling point organic solvent which has an aromatic group in the molecule and which is generally well used is used together with a polymer, a problem has been found in that the amount of the developing agent remaining after processing increases and thus causes stains in the white background part. In addition, there is another problem in the conventional technique in that the property of the coating composition containing both a cyan coupler-containing emulsion and a silver halide emulsion often varies with time after being stored. As a result, the photographic property of the photographic material obtained by coating the said coating composition cannot be kept stable. Against the problem, it has been found in the present invention that the combination of a polymer and a particular high boiling point solvent is effective. On the contrary to this, when a high boiling point solvent having an aromatic group in the molecule, such as dibutyl phthalate, is used, the intended effect cannot be obtained.